KR100449608B1 - Preparation method of styrene-based thermoplastic resin using vinyl-based mercaptan compound - Google Patents

Abstract

PURPOSE: Provided is a method for preparing a styrene-based thermoplastic resin which has a nonlinear structure, and is excellent in processability, elongation and thermal stability even with an identical molecular weight with a linear polymer. CONSTITUTION: The method comprises the steps of adding 0.0001-5 parts by weight of a vinyl-based mercaptan compound to a monomer mixture comprising 50-100 parts by weight of an aromatic vinyl compound and 0-50 parts by weight of a cyano vinyl compound, and polymerizing them. Preferably the vinyl-based mercaptan compound has a vinyl group and a mercaptan group copolymerizable with the aromatic vinyl compound or the cyano vinyl compound, and is represented by the formula II, wherein R' is H or a methyl group; and R is an alkyl group, an alkylphenyl group or an alkylhalophenyl group, and can contain an ester group or a sulfonic acid group.

Description

Manufacturing method of styrene thermoplastic resin

The present invention relates to a method for producing a styrene-based thermoplastic resin, and more particularly, to a method for producing a styrene-based thermoplastic resin having excellent appearance characteristics, excellent polymerization stability, processability, and odorless properties.

In general, styrene resins are used in styrene resins alone or general purpose resins such as ABS and HIPS because of their excellent transparency, thermal stability, and mechanical properties, and are widely commercially manufactured due to their wide application fields such as foamed resins, films, and sheets. In order to meet the same commercial requirements, a copolymer with a vinyl cyanide compound, an acryl-based compound, or an acid anhydride-based compound is formed to improve physical properties.

As a method of improving the processability of such a styrene-based thermoplastic resin, a method of changing the rheological properties by transforming a styrene-based resin having a linear structure into a nonlinear structure using a polyfunctional compound is used. Not only can increase the processability while maintaining the overall physical properties of the resin, but also improve the thermal stability during processing of the resin.

US Pat. No. 5,191,040 used a multifunctional initiator, and US Pat. No. 4,376,847 proposes a method of using a vinyl initiator as a method for preparing the styrene resin having a nonlinear structure as described above. However, these methods have a disadvantage in that contamination occurs on the inner wall of the reactor by gelation occurring during the bulk polymerization, and causes a fatal problem in the appearance of the resin after processing.

As a method for improving such a problem, US Pat. No. 5,473,031 proposes to introduce a non-linear structure into the resin by additionally adding two monomers reacting at a high temperature during copolymerization of styrene and acrylonitrile. 149912 proposes a method of using a polyfunctional compound capable of copolymerizing with a vinyl aromatic compound and a vinyl cyan compound, but a specific method for preventing a gelation problem, which may occur when synthesizing a nonlinear structure, is not shown. There is a disadvantage that the adjustment of is not easy.

In addition, in order to obtain a desired molecular weight and molecular weight distribution in the production of styrene resin, mercaptan-based chain transfer agents are generally used, and mainly t-dodecyl multicaptan or n-dodecyl multicaptan is used. However, when such a mercaptan-based chain transfer agent is used, unreacted mercaptan compounds remain in the resin after the reaction, which adversely affects the final product due to the mercury peculiar odor.

The present invention can prevent problems due to gelation and odor generated when the chain transfer agent remains when the styrene resin of the nonlinear structure is manufactured to improve the processability of the resin, and the structure of the nonlinear styrene is easy to control. It is about the manufacturing method of resin.

The present inventors earnestly studied in order to achieve the above object, and when polymerizing styrene resin, the inventors have a vinyl group copolymerizable with a vinyl monomer, and at the same time contain a mercaptan group in a molecule that can act as a chain transfer agent. When vinyl-based mercaptan is used, it is possible to prevent gelation that may occur when the polyfunctional compound is used, to remove odors caused by the remaining mercaptan, and to control the non-linear structure by controlling the amount of vinyl-based mercaptan used. The invention was devised.

More specifically, the present invention is a styrene-based polymer, characterized in that 50 to 100 parts by weight of an aromatic vinyl compound and 0 to 50 parts by weight of a vinyl cyanide compound are polymerized by adding 0.0001 to 5 parts by weight of a vinyl mercaptan compound. It is to provide a method for producing a thermoplastic resin.

As the monomer that can be used in the present invention, an aromatic vinyl compound, a vinyl cyanide compound, or the like may be used in combination with a monomer capable of whole or other copolymerization.

An aromatic vinyl compound can be represented by following General formula (I), 50-100 weight part is used.

R 'is hydrogen, a methyl group, etc., R is a phenyl group, a halophenyl group, an alkyl group, an alkylphenyl group, or an alkyl halophenyl group, Preferably it is a phenyl group. The halophenyl group is substituted with one or two halogen compounds in the phenyl group, the alkylphenyl group is substituted with one or two alkyl groups in the phenyl group, and the alkylhalophenyl group is an alkyl group containing a halogen compound or a halogen and an alkyl group substituted together. Say that.

The content of the vinyl cyanide compound is 0 to 50 parts by weight, preferably acrylonitrile, methacrylonitrile, etaacrylonitrile alone or a mixture thereof.

In addition, in order to improve the properties of the copolymer, esters such as acrylic acid esters and methacrylic acid esters, imides such as maleimide and N-phenylmaleimide, acid anhydrides such as maleic anhydride, etc. Ethylenically unsaturated monomers can be used in the range of 0 to 20 parts by weight.

The initiator used in the present invention is azo initiator, 2-t-butyl azocyanopropane, butyl azocyanobutane, 1-t-butyl azo-1-cyanocyclohexane, dimethyl-2,2'-azobis Isobutyrate, 2,2'-azobisisobutyrate, 2,2'-azobis-isobutyronitrile, 1,1'-cyclohexylcarbonitrile, 2,2'-azobis-2-methyl-butyro Nitrile, azobis- (4-cyanobalic acid) and the like. In the case of using such an azo polymerization initiator, it is possible to prevent oxidation due to nitrogen generated when the initiator is decomposed to generate radicals, and thus there is an advantage in that discoloration during polymerization can be suppressed to some extent.

When starting polymerization using an azo initiator, a styrene resin of desired physical properties can be produced by using an initiator having a half-life temperature of 80 to 100 ° C for 10 hours. Since the initiator having a half-life temperature of 80 ° C. or less for 10 hours is required in large quantities for the activation of the monomer, even when the polymerization is completed at an appropriate conversion rate, the molecular weight is significantly lowered to achieve the desired physical property level.

In addition to the azo initiator, a peroxide initiator having a 10-hour turn-on temperature of 80 to 100 ° C. may be used. Such peroxide initiators may be benzoyl peroxide, dicumyl peroxide, di-t-butyl-peroxyhexahydroterephthalate, t -Butyl-peroxybenzoate, 2,5-dimethyl-2,5'-di- (benzoylperoxy) -hexane, 1,1'-di- (t-butylperoxy) -cyclohexane, 1,1 '-Di- (t-butylperoxy) -3,3', 5-trimethylcyclohexane and the like have a disadvantage that the color is slightly yellow compared to the case of using an azo initiator.

Vinyl-based mercaptan that can be used as a non-linear center in the present invention has a structure such as the following formula (II).

Here, R 'is hydrogen, a methyl group and the like, R is an alkyl group, an alkylphenyl group or an alkyl halophenyl group, and may include an ester group and a sulfonic acid group, preferably an alkylphenyl group. In this case, the vinyl mercaptan may be used alone or in combination of two or more vinyl mercaptans.

When a polyfunctional monomer is used to prepare a styrene resin having a nonlinear structure, it is difficult to precisely control the structure of the resin to obtain a desired structure, and as a result, it is difficult to control the balance of physical properties. In addition, the gelation occurs due to the crosslinking structure, causing contamination of the inner wall of the reactor, which causes surface defects of the final resin.

Therefore, by using the vinyl mercaptan according to the present invention during styrene resin polymerization, it is possible to prevent deterioration of polymerization stability such as gel generation and reactor inner wall contamination, and since the compound contains a reactive group such as vinyl group, the styrene resin Participation in the reaction during the production can be eliminated odor generation of the resin by the unreacted mercaptans appearing when using a molecular weight regulator of dodecyl multicaptans such as t- dodecyl multicaptan and n- dodecyl multicaptan. The total amount of mercaptan used to prepare the non-linear styrene resin is 0.0001 to 5 parts by weight, preferably 0.01 to 3 parts by weight. By controlling the amount of use of such vinyl-based mercaptan, it is possible to obtain a nonlinear structure of a desired degree.

The polymerization reaction of the styrene resin is generally performed at 50 to 150 ° C, preferably at 80 to 100 ° C, over 3 to 40 hours. The polymerization can be continuous block polymerization, emulsion polymerization, suspension polymerization, and the vinyl-based mercaptan compound can be introduced at the beginning of the polymerization or during the polymerization reaction, or can be added intermittently or continuously.

In general, the weight average molecular weight of the polymer is 50000 to 500000, preferably 70000 to 350000. In particular, the use of vinyl-based mercaptan allows arbitrarily control of molecular weight, molecular weight distribution and degree of nonlinearity, and the processability is remarkably excellent compared to linear resins having the same molecular weight without deterioration of impact resistance exhibited in non-linear resins.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited by the following Examples.

The parts in the following Examples and Comparative Examples are based on weight.

Examples 1-6

500 ml reactor equipped with a stirrer and a baffle and nitrogen-substituted 200 parts of ion-exchanged water, 0.4 parts of tricalcium phosphate, 0.03 parts of carboxylic acid anionic surfactant, 0.01 parts of polyoxyethylene alkyl ether phosphate ester, 2,2'- 0.11 parts of azobisisobutyronitrile, 71 parts of styrene, 29 parts of acrylonitrile, 0.05 parts of sodium dodecylbenzenesulfonate, and vinyl mercaptan were added in varying structures and dosages as shown in Table 1 below. It was completely sealed and given sufficient stirring power. After confirming the dispersion, the temperature inside the reactor was raised to 75 ° C. to initiate the reaction, and the reaction was carried out for a total of 4.5 hours. After the completion of the polymerization, the produced polymer was dried to prepare styrene resin beads, and then the analysis results were displayed. 1 is shown.

Comparative Examples 1 to 6

Under the same conditions as in Examples 1 to 6, only t-dodecyl mercaptan and divinylbenzene were added without polymerization of the vinyl mercaptan. Table 2 shows the content and analysis results of t-dodecyl multicaptan (A) and divinylbenzene (B) added during the polymerization.

A: t-dodecyl mulcaptan

B: divinylbenzene

Property evaluation method

1) Weight average molecular weight: measured by gel chromatography.

2) Flowability: Measured by melt index at 5 kg.

3) Impact resistance: measured by ASTM D256-notched specimen (thickness: 1/8 inch).

4) Polymerization Stability: The degree of stirring during polymerization was visually determined.

○: Good △: Normal ×: Poor

5) Gel number: After the polymer was produced into a sheet having a thickness of 1 mm, a gel number of 1 mm or more in diameter was measured in a 10 cm x 1 m sheet.

6) Resin smell: measured by organoleptic test.

7) *: No measurement

For Examples 1 to 6 resins using vinyl-based mercaptans in Table 1, the gel number serving as a criterion for appearance was compared to Comparative Examples 1 to 6 in which dodecyl mercaptan (A) and divinylbenzene (B) were mixed. It is small and it can be seen that the state of the inner wall of the reactor is also good. In addition, the smell of the resin by the sensory test method was also good, and the molecular weight distribution is small, it is possible to prepare a resin with improved physical properties while preventing the physical properties due to the wide molecular weight distribution.

As described above, the styrene resin prepared according to the present invention has a nonlinear structure different from that exhibited by the linear polymer by using an appropriate amount of vinyl-based mercaptan compound in the polymerization, and in particular, has the same molecular weight as the linear polymer. It is possible to produce a styrene resin exhibiting excellent processability, stretching properties and thermal stability.

Claims (3)

In the polymerization of the styrenic copolymer with 50 to 100 parts by weight of the aromatic vinyl compound and 0 to 50 parts by weight of the vinyl cyanide compound, 0.0001 to 5 parts by weight of the vinyl mercaptan compound is added to polymerize the styrene-based thermoplastic resin. Manufacturing method. The styrene-based thermoplastic resin according to claim 1, wherein the vinyl-based mercaptan compound has a vinyl group and a mulcaptan group copolymerizable with an aromatic vinyl compound or a vinyl cyanide compound, and has a structure of Formula (II). Way.

Here, R 'is hydrogen or a methyl group, R is an alkyl group, an alkylphenyl group or an alkyl halophenyl group, and may include an ester group or a sulfonic acid group. The method of claim 1 or 2, wherein the vinyl-based mercaptan compound is used alone or in a mixture of two or more.